1. Field of the Invention
The present invention relates to a multilayer barrier film structure, and an organic electroluminescent display panel and a manufacturing method thereof.
2. Description of the Related Art
Organic electroluminescent display panels (hereinafter referred to as “organic EL display panels”) in which a plurality of organic electroluminescent devices (hereinafter referred to as “organic EL devices”) are formed on a supporting substrate have been developed to be used in display apparatuses.
An organic EL device is a luminescent device comprising at least one thin film (hereinafter referred to as the “organic functional layer”) including a light-emitting layer made of an organic material that is electroluminescent, i.e., emits light upon an electrical current being injected therein. With such an organic EL device, basically, the organic functional layer is sandwiched between an anode and a cathode, excitons are formed when electrons and holes injected from the two electrodes recombine, and light is produced when these excitons return from the excited state to the ground state.
There is a problem that if such an organic EL device is exposed to the atmosphere, then the organic EL device is affected by infiltration of molecules of oxygen, water and the like, and hence there is a marked deterioration in light emission characteristics such as brightness and color. To prevent this infiltration, a method has been proposed in which an inorganic film is formed on the organic EL device to block penetrating moisture and the like. Furthermore, as disclosed in WO 00/36665, a so-called multilayer gas barrier film in which inorganic films predominantly responsible for gas barrier ability and resin films are formed alternately (i.e., the resin films are inserted between the inorganic films) has been proposed. Here, “gas barrier ability” refers to a property of acting as a barrier to the permeation of oxygen and moisture; if the number of molecules of oxygen, water and the like that permeate through is high, then the gas barrier ability is low, and if the number of molecules of oxygen, water and the like that permeate through is low, then the gas barrier ability is high. The gas barrier ability of a multilayer gas barrier film is affected by the gas barrier ability of each film itself, and is also greatly affected by the density of defects such as pinholes. When the inorganic films are compared in the gas barrier ability with that of the resin films, the inorganic films exhibit a gas barrier ability higher than the resin films in general. However, the inorganic films are formed using a dry film formation method such as vacuum deposition or sputtering, and hence local defects such as pinholes are prone to occur.
With a multilayer gas barrier film comprising inorganic films and resin films, the effect of pinholes and the like in a single inorganic film layer can be reduced. However, even with a multilayer gas barrier film, if all of the layers are formed using a dry film formation method, then defects present in the first layer affect the next layer, and hence it is difficult to reduce the density of defects such as pinholes. Moreover, resin layers having a low gas barrier ability will be exposed at edge faces of the multilayer gas barrier film, and hence moisture and the like will infiltrate in via the edge face parts of the resin layers, and thus the merits of using a multilayered structure will not be realized to the full.
There can be envisaged in advance a method in which the edge face parts of the resin layers in the multilayer gas barrier film are covered with the inorganic films. But manufacturing specifications of such method would have to be changed such as preparing predetermined masks of various sizes with the area of the resin layers being changed in accordance with the number and shapes of various inorganic films, and hence this method would be inefficient from a manufacturing perspective.